Parallel RCM mechanism end effector for orthopedic surgery

Abstract

The application discloses a parallel RCM mechanism end effector for orthopedic surgery, which comprises two motors, three movement units, a double parallelogram linkage mechanism and a ball mill. The two motor axes are perpendicular and are installed on a base. The motor A is hingedly connected to the bottom end of the first movement unit; the motor B is hingedly connected to the bottom end of the second movement unit; the third movement unit is symmetrically arranged with the second movement unit and is hingedly connected to the base at the bottom end. The upper rod end of the double parallelogram linkage mechanism is hingedly connected to the top end of the second and third movement units through a rotating shaft; the lower rod end is hingedly connected to the three movement units through a rotating shaft. The upper rod and the lower rod are rotationally connected to the ball mill at the front ends. The double parallelogram linkage mechanism is used to make the center of the ball mill head coincide with the fixed point of the RCM mechanism, and the mechanism characteristic of the fixed point of the RCM mechanism is utilized. The fixed point is made to coincide with the ball center of the ball mill head, so that the position of the ball mill head is unchanged when the posture of the ball mill is changed, the posture of the ball mill does not affect the grinding process in the grinding process, the posture of the ball mill can be adjusted, the obstacle avoidance can be better realized, and the safety is improved.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, specifically to a parallel RCM mechanism end effector for orthopedic surgery. Background Technology

[0002] Total knee replacement surgery involves surgically implanting an artificial knee joint into the patient's body to replace the function of the diseased knee joint, thereby relieving joint pain and restoring joint function. As a type of orthopedic surgery, knee replacement surgery is a deep surgery with a complex internal structure. Since the object of the operation is a rigid bony structure, it requires a high degree of precision and rigidity in the operation, and the surgical techniques are complex and diverse.

[0003] Knee replacement surgery robots can assist or replace doctors in performing knee replacement surgery. They have functions such as preoperative planning, navigation and positioning, precise control of the actuator, and real-time analysis of joint force lines. Patients who undergo surgery using these robots have lower limb force lines that are closer to normal, effectively improving the surgical outcome of joint replacement.

[0004] The design of the end effector configuration for joint replacement surgery robots is one of the key issues in robotic systems. The end effector of a knee replacement surgery robot must accurately grind the planned bone area, protect the surgical incision and soft tissue, facilitate surgical manipulation, and not obstruct the surgeon's field of vision. The design of the mechanism must also consider its interaction with the surgeon and the surgical site, achieving lightweight and miniaturization while meeting flexibility, safety, and maneuverability requirements, and satisfying hygienic conditions for surgical use. Summary of the Invention

[0005] To address the aforementioned issues, this invention proposes a parallel RCM mechanism end effector for orthopedic surgery, designed to meet the requirements of minimally invasive surgery in knee replacement surgery, such as relatively small incisions, grinding in confined spaces, soft tissue protection, and high precision of surgical pathways.

[0006] An end effector of a parallel RCM mechanism for orthopedic surgery includes three motion units driven by two drive modules; the three motion units are connected to the rear side of a double parallelogram linkage mechanism, and the front side of the double parallelogram linkage mechanism is connected to a ball milling tool.

[0007] The output ends of the two drive modules are vertically arranged. One drive module's output end is hinged to the bottom of the first motion unit via a connector, with the hinge axis perpendicular to the drive unit's output end. The other drive module's output end is hinged to the bottom of the second motion unit via a connector, with the hinge axis perpendicular to the drive unit's output end. The third motion unit is symmetrically arranged with the second motion unit, and its bottom end is hinged to the bracket via a connector, with the hinge axis parallel to the hinge axis at the hinge point of the second motion unit.

[0008] The aforementioned double parallelogram linkage mechanism includes an upper link and a lower link. The ends of the upper link are hinged to the tops of the second and third motion units via connecting members, and also have a revolute joint that rotates about the perpendicular bisector of the hinge axis. The end of the lower link is hinged to the top of the second motion unit via a connecting member, and also has a revolute joint that rotates about the perpendicular bisector of the hinge axis. Simultaneously, the middle sections of the lower link are hinged to connecting rods fixed in the middle of the second and third motion units, and also have a revolute joint that rotates about the perpendicular bisector of the hinge axis; the axes of all the aforementioned hinge axes are perpendicular to the plane formed by the connected links.

[0009] In the above-mentioned double parallelogram linkage mechanism, the front ends of the upper and lower rods are respectively hinged to the clamping part of the ball milling mold, and the axis of the hinge shaft is parallel to the axis of the top hinge shaft of the first motion unit; at the same time, it has a rotating pair that rotates about the vertical line of the hinge shaft.

[0010] Driven by two drive modules, three motion units are linked with the double parallelogram linkage mechanism, ultimately achieving attitude adjustment of the ball grinding tool mounted at the front end of the double parallelogram linkage mechanism, while the center position of the ball grinding head of the ball grinding tool is fixed during the attitude adjustment process.

[0011] The advantages of this invention are:

[0012] 1. The parallel RCM mechanism end effector of the present invention for orthopedic surgery, through three identical motion units connected in parallel, has higher accuracy and stability compared to serial mechanisms;

[0013] 2. The parallel RCM mechanism end effector of the present invention for orthopedic surgery achieves decoupling of end effector posture and robotic arm movement through the designed RCM mechanism, optimizes the control method, and improves control accuracy;

[0014] 3. The parallel RCM mechanism end effector of the present invention for orthopedic surgery, through the design of a double parallelogram mechanism, makes the distal fixed point of the RCM mechanism located outside the main body of the mechanism, which solves the problem of the mechanism affecting the doctor's field of vision and improves the working space and dexterity of the mechanism. Attached Figure Description

[0015] Figure 1 This is a side view of the overall structure of the end effector of the parallel RCM mechanism of the present invention;

[0016] Figure 2 This is a top view of the overall structure of the parallel RCM mechanism end effector of the present invention;

[0017] Figure 3 This is a perspective view of the overall structure of the end effector of the parallel RCM mechanism of the present invention;

[0018] Figure 4This is a schematic diagram of the Type II connector structure in the end effector of the parallel RCM mechanism of the present invention;

[0019] Figure 5 This is a schematic diagram of the I-shaped connector structure in the end effector of the parallel RCM mechanism of the present invention;

[0020] Figure 6 This is a schematic diagram of the ball mill connection structure in the end effector of the parallel RCM mechanism of the present invention;

[0021] Figure 7 This is a schematic diagram of the double parallelogram linkage mechanism formed by the double parallelogram linkage in the end effector of the parallel RCM mechanism of the present invention.

[0022] In the picture:

[0023] 1-Base 2-Double parallelogram linkage mechanism 3-Ball abrasive mold

[0024] 4-First motion unit 5-Second motion unit 6-Third motion unit 7-Type I connector 8-Type II connector 1a-Motor module A

[0025] 1b-Motor Module B a-Arc-shaped rod b-Arc-shaped rod c-Straight rod d-Short straight rod 201-Upper straight rod

[0026] 202-Lower Straight Rod; 203-Upper Rod Extension; 204-Lower Rod Connector; 301-Clamping Part; 302-Mold Part; 303-U-shaped Connector Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings.

[0028] This invention relates to a parallel RCM mechanism end effector for orthopedic surgery, comprising a base 1, a double parallelogram linkage mechanism 2, a ball mill 3, a first motion unit 4, a second motion unit 5, a third motion unit 6, and a drive unit, as follows: Figures 1-3 As shown.

[0029] The drive unit includes two motor modules, denoted as motor module A1a and motor module B1b. Both motor modules A1a and B1b are mounted on the base 1. Motor module A1a has its axis aligned along the front-to-back direction. The motor mounting base at the end of the motor module A1a is fixed to the body end of the base 1 by screws, and its output end is connected to an I-type connector 7 via an opening on the motor mounting base. Furthermore, the I-type connector 7 connects to the first motion unit 4.

[0030] The axis of motor module B1b is perpendicular to the axis of motor module A1a and is positioned in the left-right direction. The body end of motor module B1b is fixedly connected to the motor mounting bracket designed on the front left side of base 1. The output end of motor module B1b is connected to the type I connector 7 through the opening on the motor mounting plate, and further connected to the second motion unit 5 through the type I connector 7. A motion unit connecting seat is designed on the front right side of base 1, and a type II connector 8 is installed on the motion unit connecting seat to connect the third motion unit 6.

[0031] The aforementioned Type II connector 8 is a T-type connector; one independent end connects to the center of the connecting plate, and the opposite two ends are used to connect the motion unit, such as... Figure 4 As shown; Type I connector 7 is a T-type connector with a bottom connecting plate; the connecting plate is coaxially fixed to the motor output end; the opposite ends are used to connect the motion unit, such as... Figure 5 As shown.

[0032] The first motion unit 4 includes two arc-shaped rods, denoted as arc-shaped rod a and arc-shaped rod b, and a straight rod c. Arc-shaped rods a and b have their inner arcs facing each other and are each composed of two parallel arc-shaped plates. One end of arc-shaped rods a and b is a fixed end, respectively fixed to both ends of the straight rod c; when fixed, the end of the straight rod c is placed between the two arc-shaped plates, and the three are fitted together and tightened with screws. The other end of arc-shaped rods a and b is a hinged end. The hinged end of arc-shaped rod a is connected to an I-shaped connector 7 on the output end of motor module A1a; when connected, the opposite ends of the I-shaped connector 7 are placed between the two arc-shaped plates, and the two arc-shaped plates are connected by bearings to form a rotating pair; the hinged end of arc-shaped rod b is used to connect to the double parallelogram mechanism 2.

[0033] The structures of the second motion unit 5 and the third motion unit 6 are basically the same as those of the first motion unit 4, both including two arc-shaped rods and a long straight rod c. The difference is that in the second motion unit 5 and the third motion unit 6, a short straight rod d is also installed on the long straight rod c. The short straight rod d consists of two parallel rods, which are set perpendicular to the long straight rod c and are fixed to the long straight rod c at their ends. When fixed, the two parallel rods of the short straight rod d are located on both sides of the long straight rod c, and are attached to the long straight rod c and the three are tightened and fixed by screws.

[0034] In the second motion unit 5, the hinged end of the arc-shaped rod a is connected to the I-shaped connector 7 on the output end of the motor module B1b via a bearing, in the same way as the connection between the arc-shaped rod a and the I-shaped connector 7 in the first motion unit 4. In the second motion unit 5, the hinged ends of the arc-shaped rod b and the short straight rod d are used to connect to the double parallelogram linkage mechanism 2.

[0035] In the third motion unit 6 mentioned above, the hinged end of the arc-shaped connecting rod a is connected to the II-shaped connecting piece 8 on the right side of the base 1 via a bearing, and the connection method is the same as that between the arc-shaped rod a and the I-shaped connecting piece 7 in the first motion unit 4. In the third motion unit 6, the hinged ends of the arc-shaped rod b and the short straight rod d are used to connect to the double parallelogram linkage mechanism 2.

[0036] Both ends of the aforementioned short straight rod d are rounded to prevent interference or collision with the double parallelogram linkage mechanism 2 during movement;

[0037] The double parallelogram linkage mechanism 2 includes an upper straight rod 201 and a lower straight rod 202 that are parallel to each other. The end of the upper straight rod 201 is connected to the second motion unit 5 and the third motion unit 6 via an upper rod extension 203. The end of the lower straight rod 202 is connected to the first motion unit 4, the second motion unit 5, and the third motion unit 6 via a lower rod connector 204.

[0038] The upper rod extension 203 is a straight rod with its axis perpendicular to the upper straight rod 201. A slot is cut in the middle of the upper rod extension 203, and the end of the upper straight rod 201 is placed within the slot and fixed to the upper rod extension 203 by loosening bolts, forming a T-shaped integral structure. Both ends of the upper rod extension 203 are designed with connecting surfaces, which are respectively connected to the hinged ends of the arc-shaped rods b in the second motion unit 5 and the third motion unit 6 via II-shaped connectors 8. During connection, one independent end of the II-shaped connector 8 is connected to the connecting surface via a bearing to form a rotating pair; the opposite ends are respectively connected to the two arc-shaped plates in the arc-shaped rod b via bearings to form rotating pairs.

[0039] The lower rod connector 204 is a T-shaped rod with a slot in the middle of one side where the two ends are located. The end of the lower straight rod 202 is placed in the slot and fixed to the slot with bolts. All three ends of the lower rod connector 204 are designed with connecting surfaces, which are respectively connected to the hinged ends of the arc-shaped rod b in the first motion unit 4 and the short straight rod d in the second motion unit 5 and the third motion unit 6 via II-shaped connectors 8. During connection, one independent end of the II-shaped connector 8 is connected to the connecting surface via a bearing to form a rotating pair; the two opposite ends are respectively connected to the two arc-shaped plates in the arc-shaped rod b and the two parallel rods in the short straight rod d via bearings to form rotating pairs.

[0040] The front ends of the aforementioned upper straight rod 201 and lower straight rod 202 are used to connect the ball milling mold 3. For example... Figure 6As shown, the ball milling tool 3 includes a clamping part 301 and a grinding part 302. The clamping part 301 is used to hold and fix the grinding part 302, and includes a front gripper for holding the front and rear parts of the grinding part 302. The ball milling tool 3 is connected to the front ends of the upper straight rod 201 and the lower straight rod 202 via U-shaped connectors 303. Specifically, the two ends of the front of the two U-shaped connectors 303 are designed with connecting shafts, which are connected to the circumferentially opposite positions of the rear and front parts of the clamping part in the ball milling tool 3 via bearings, forming a rotating pair. The center of the ends of the two U-shaped connectors 303 are provided with connecting shafts, which are connected to the connecting surfaces designed at the front ends of the upper straight rod 201 and the lower straight rod 202 via bearings, forming a rotating pair. The clamping part 303 of the ball milling tool 3 is rotatably connected to the upper straight rod 201 and the lower straight rod 202 of the double parallelogram linkage mechanism 2. The aforementioned upper straight rod 201, the second motion unit 5, and the ball milling mold 3 together constitute a double parallelogram structure, as shown below. Figure 7 As shown in the dashed box, the center of the ball grinding head of the ball grinding tool 3 is located at one end of the double parallelogram.

[0041] In the above structure, the output end of the motor module A1a drives the first motion unit 4 to move around the axis of the output end of the motor module A1a through the I-type connector 7; then the first motion unit 4 can drive the lower rod connector 204 of the double parallelogram mechanism 2 to move in the left and right directions, and always keep its plane parallel to the base 1 during the movement.

[0042] The output end of the second motor module 106 drives the second motion unit 5 to move around the output end axis via the I-type connector 7; in turn, the second motion unit 5 drives the upper extension rod 203 in the double parallelogram mechanism 2 to move in the front-back direction. During the process, the third motion unit 6 moves accordingly, and since the third motion unit 6 is a symmetrical structure of the second motion unit 5, the upper straight rod 201 and the lower straight rod 202 in the double parallelogram mechanism 2 are always parallel.

[0043] Since the center of the grinding head of the ball milling tool 3 is located at one end of the double parallelogram formed by the upper straight rod 201, the second motion unit 5, and the ball milling tool 3, the position of the center of the grinding head of the ball milling tool 3 remains unchanged during the above-mentioned motion process; only the posture of the ball milling tool 3 can be changed.

[0044] The parallel RCM mechanism end effector described above changes the length of the upper straight rod 201 in the double parallelogram mechanism 2, thereby changing the position of the far-end fixed point, i.e. the center of the ball mill head, making the movement more flexible.

[0045] In summary, the parallel RCM mechanism end effector of this invention, through a double parallelogram linkage mechanism 2, ensures that the center of the grinding head coincides with the fixed point of the RCM mechanism, utilizing the mechanism characteristic of the RCM mechanism where one point remains stationary. By aligning the fixed point with the center of the grinding head, the position of the grinding head remains unchanged when the grinding wheel's posture changes. This decouples the grinding wheel's position from its posture, simplifying the complexity of posture control and improving its motion flexibility. It ensures that the grinding wheel's posture does not affect the grinding process, allowing for posture adjustment and better obstacle avoidance, thus enhancing safety.

Claims

1. An end effector for a parallel RCM mechanism used in orthopedic surgery, characterized in that: It includes three motion units driven by two drive modules; the three motion units are connected to the rear side of the double parallelogram linkage mechanism, and the front side of the double parallelogram linkage mechanism is connected to the ball grinding mold; The output shafts of the two drive modules are vertically arranged. One drive module's output shaft is hinged to the bottom of the first motion unit via a connector, with the hinge axis perpendicular to the drive unit's output shaft. The other drive module's output shaft is hinged to the bottom of the second motion unit via a connector, with the hinge axis perpendicular to the drive unit's output shaft. The third motion unit is symmetrically arranged with the second motion unit, its bottom end hinged to the bracket via a connector, with the hinge axis parallel to the hinge axis of the second motion unit. The first motion unit includes two arc-shaped rods and a long straight rod. The inner arcs of the two arc-shaped rods are arranged opposite each other, and their fixed ends are respectively fixed to both ends of the straight rod. The hinged ends are connected to a double parallelogram linkage mechanism. The second and third motion units have the same structure as the first motion unit, and short straight rods perpendicular to the long straight rods in the middle of the second and third motion units are installed. The aforementioned double parallelogram linkage mechanism includes an upper link and a lower link; the upper link includes an upper straight link and an upper extended connecting link; the lower link includes a lower straight link and a lower extended connecting member. In the upper rod, the upper extension connecting rod is a straight rod, and the end of the upper straight rod is fixed to the middle of the vertically set extension connecting rod; the two ends of the extension connecting rod are designed with connecting surfaces to connect the top of the second motion unit and the third motion unit, and at the same time have a rotating pair that can rotate about the vertical line of the hinge axis; In the lower rod, the lower extension connecting rod is a T-shaped rod, with its opposite ends located on one side perpendicular to the lower straight rod, and its middle part fixed to the end of the lower straight rod; the lower extension connecting rod has connecting surfaces at all three ends, with the connecting surfaces at opposite ends connecting to the short straight rods on the second and third motion units, and also having a revolute joint that rotates about the perpendicular line of the hinge axis; the connecting surface at the other end connects to the top of the first motion unit, and also has a revolute joint that rotates about the perpendicular line of the hinge axis; the axes of the aforementioned hinge axes are all perpendicular to the plane formed by the connected rods; The aforementioned connectors include two structures to achieve the corresponding connection, including Type of connector and Type of connector; wherein, the connection between the drive module and the rod adopts Type of connector; The connector is a type with two perpendicular axes. One connector has a connecting disc at its end that connects to the output of the drive module; the other connector connects to the motion unit; the remaining connectors all use... Type of connector; The type connector also has two mutually perpendicular connecting ends; one end connects to a rod to form a revolute joint; the other end connects to a motion unit. In the above-mentioned double parallelogram linkage mechanism, the front ends of the upper and lower rods are respectively hinged to the clamping part of the ball milling mold, and the axis of the hinge shaft is parallel to the axis of the top hinge shaft of the first motion unit; at the same time, it has a revolute pair that rotates about the vertical line of the hinge shaft. Driven by two drive modules, three motion units are linked with the double parallelogram linkage mechanism, ultimately achieving attitude adjustment of the ball grinding tool mounted at the front end of the double parallelogram linkage mechanism, while the center position of the ball grinding head of the ball grinding tool is fixed during the attitude adjustment process.

2. The parallel RCM mechanism end effector for orthopedic surgery as described in claim 1, characterized in that: The two curved members and the short straight member are all composed of two parallel plates; at the same time, when connecting the members, one end of the connector is designed to be placed between the parallel plates and hinged to the two parallel plates.

3. The parallel RCM mechanism end effector for orthopedic surgery as described in claim 1, characterized in that: The upper and lower rods are connected to the clamping part of the ball mill through U-shaped connectors. Specifically, the two ends of the front of the two U-shaped connectors are designed with connecting shafts, which are respectively hinged to the opposite side of the end and middle of the clamping part of the ball mill; at the same time, the center position of the end of the U-shaped connector is connected to the front of the upper and lower rods to form a rotating pair.

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